FRIDAY, March 17, 2017 (HealthDay News) -- U.S. veterans with substance abuse problems have a higher risk of suicide than veterans who don't, new research suggests.

The study looked at more than 4 million veterans, and found that drug or alcohol problems affected 8 percent of males and 3 percent of females. These veterans had a more than twofold increased risk of suicide compared with those without a substance use disorder.

The suicide rate was especially high among female veterans with drug or alcohol problems. These women had a more than five times greater rate of suicide than female veterans who did not have substance abuse problems.

"We hope these findings will help clinicians and health systems care for people with substance use disorders, with mental health conditions, and with both -- and focus suicide prevention efforts accordingly," said lead study author Kipling Bohnert.

Bohnert is an assistant professor of psychiatry at the University of Michigan Medical School, and also a researcher with the VA Center for Clinical Management Research.

Each day, 20 U.S. veterans die by suicide, the researchers said, a rate much higher than in the general population.

"Substance use disorders may be important markers for suicide risk," Bohnert said in a university news release.

The study found that suicide risk among veterans differed by type of substance abuse. The highest risks were among those who abuse prescription sedative medicines, such as tranquilizers.

Female veterans were more at risk if they abused opioid painkillers, while males had an increased suicide risk if they abused amphetamines, the findings showed.

The study, published online March 16 in the journal Addiction, highlights the need to direct more veterans' suicide prevention efforts to those with drug or alcohol problems.

Two-thirds of the suicides in the study involved firearms, so gun safety needs to be a major part of efforts to reduce suicides among veterans. In addition, Bohnert and colleagues found that one-quarter of suicides by veterans with substance use disorders were by intentional poisoning, so strategies to prevent that form of suicide are also needed.